DESCRIPTION (Applicant's abstract): Despite recent data showing an overall decrease in mortality from breast cancer, breast cancer mortality rates remain high, particularly among older women. Geographic differences in the breast cancer mortality of older women appear at least partially attributable to survival differences, a finding which implicates cancer control practices. There is much evidence that older women with breast cancer receive less appropriate care than younger women. One factor, which has been shown to influence outcomes of some disease processes, is provider experience, usually measured as the volume of cases seen at a given hospital or handled by a given physician. In this application, we propose to investigate the relationship between breast cancer outcomes and provider volume of cases, in a cohort of older breast cancer patients. The specific aims of this proposal are, among a cohort of SEER patients aged 65 and older, who were treated for early stage breast cancer and for whom Medicare claims are available, to: 1. Determine the treatment hospital and other relevant hospital characteristics (size, urban vs rural status, teaching status, availability of special facilities) for patients in the cohort treated at inpatient or outpatient hospital-based surgical centers. 2. Determine the treating surgeon and other relevant physician characteristics (age, year of medical school, graduation, gender, specialty and board certification). 3. Determine the annual volume of older breast cancer patients treated by each hospital and surgeon treating patients in the cohort. 4. Assess the relationship of annual hospital volume and annual surgeon volume to outcomes of overall 5-year survival, 5-year survival from breast cancer, and 5-year survival free of treatment of recurrent disease.